Pay-as-you-go Oyster cards in London will be valid on the city’s suburban overland rail network by early 2010, officials have said.

An official announcement for the card’s launch, which has been delayed by months, for trips on all National Rail stations across the city is expected in a few weeks.

The Oyster card is a permanent reusable electronic ticket, which is topped up from time to time by its owner.

Currently, the smartcard system can be used on the London Overground network, the tube, buses, trams and the Docklands Light Railway service.